Hi, I can’t restore Grub, it seems to me that boot/efi is corrupted.
manjaro-chroot -a
==> Detected systems:
--> 0) Ubuntu
--> 1) ManjaroLinux
==> Select system to mount [0-1] :
1
==> Mounting (ManjaroLinux) [/dev/sda7]
--> mount: [/mnt]
--> mount: [/mnt/boot/efi]
mount: /mnt/boot/efi: special device /dev/disk/by-uuid/F1D6-9A8A does not exist.
dmesg(1) may have more information after failed mount system call.
--> mount: [/mnt/home]
[manjaro /]# grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=manjaro --recheck
Installing for x86_64-efi platform.
grub-install: error: /boot/efi doesn't look like an EFI partition.
[manjaro /]#
It does not found a partition with that UUID, so you don’t even have a partition mounted at /boot/efi. What’s the output of:
lsblk -f
and
fdisk -l
[manjaro /]# lsblk -l
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
loop0 7:0 0 66.9M 1 loop
loop1 7:1 0 1.2G 1 loop
loop2 7:2 0 1.7G 1 loop
loop3 7:3 0 929.9M 1 loop
sda 8:0 0 238.5G 0 disk
sda1 8:1 0 100M 0 part
sda2 8:2 0 16M 0 part
sda3 8:3 0 58.9G 0 part
sda4 8:4 0 521M 0 part
sda5 8:5 0 512M 0 part
sda6 8:6 0 4G 0 part
sda7 8:7 0 40G 0 part /
sda8 8:8 0 100G 0 part /home
sda9 8:9 0 1.1G 0 part
sda10 8:10 0 33.4G 0 part
sdb 8:16 1 7.2G 0 disk
sdb1 8:17 1 7.2G 0 part
sdb2 8:18 1 32M 0 part
sr0 11:0 1 1024M 0 rom
ventoy 254:0 0 3.9G 1 dm
[manjaro /]# fdisk -l
Disk /dev/sda: 238.47 GiB, 256060514304 bytes, 500118192 sectors
Disk model: Intenso SSD Sa
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 992BA2A6-96BD-4E8E-932F-CD3742394EC8
Device Start End Sectors Size Type
/dev/sda1 2048 206847 204800 100M EFI System
/dev/sda2 206848 239615 32768 16M Microsoft reserved
/dev/sda3 239616 123662335 123422720 58.9G Microsoft basic data
/dev/sda4 123662336 124729343 1067008 521M Windows recovery environment
/dev/sda5 124731392 125779966 1048575 512M EFI System
/dev/sda6 489484288 497872895 8388608 4G Linux swap
/dev/sda7 125779968 209666047 83886080 40G Linux filesystem
/dev/sda8 209666048 419381247 209715200 100G Linux filesystem
/dev/sda9 497872896 500097023 2224128 1.1G Windows recovery environment
/dev/sda10 419381248 489484287 70103040 33.4G Linux filesystem
Partition table entries are not in disk order.
Disk /dev/sdb: 7.2 GiB, 7736072192 bytes, 15109516 sectors
Disk model: DataTraveler 3.0
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xe1d2cc2e
Device Boot Start End Sectors Size Id Type
/dev/sdb1 * 2048 15043975 15041928 7.2G 7 HPFS/NTFS/exFAT
/dev/sdb2 15043976 15109511 65536 32M ef EFI (FAT-12/16/32)
Disk /dev/mapper/ventoy: 3.89 GiB, 4173903872 bytes, 8152156 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x00000000
Device Boot Start End Sectors Size Id Type
/dev/mapper/ventoy-part1 * 64 8143963 8143900 3.9G 0 Empty
/dev/mapper/ventoy-part2 8143964 8152155 8192 4M ef EFI (FAT-12/16/32)
Disk /dev/loop0: 66.9 MiB, 70148096 bytes, 137008 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/loop1: 1.16 GiB, 1244356608 bytes, 2430384 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/loop2: 1.68 GiB, 1798864896 bytes, 3513408 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/loop3: 929.89 MiB, 975060992 bytes, 1904416 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
[manjaro /]#
Gracias, pero fíjate bien, es lsblk -f (letra f, no l)
Ya que estamos también puedes dar la salida de blkid
Edit: Sorry, I mixed threads 
English translation:
Thanks, but notice that it is lsblk -f (letter f, not l)
You can also provide the output of blkid
[manjaro /]# lsblk -f
NAME FSTYPE FSVER LABEL UUID FSAVAIL FSUSE% MOUNTPOINTS
loop0
loop1
loop2
loop3
sda
|-sda1
|-sda2
|-sda3
|-sda4
|-sda5
|-sda6
|-sda7 25.8G 29% /
|-sda8 62.8G 31% /home
|-sda9
`-sda10
sdb
|-sdb1
| `-ventoy
`-sdb2
sr0
[manjaro /]# blkid
/dev/loop1: TYPE="squashfs"
/dev/sdb2: SEC_TYPE="msdos" LABEL_FATBOOT="VTOYEFI" LABEL="VTOYEFI" UUID="C559-2E5D" BLOCK_SIZE="512" TYPE="vfat" PARTUUID="e1d2cc2e-02"
/dev/sdb1: LABEL="Ventoy" UUID="BC9E-47E4" BLOCK_SIZE="512" TYPE="exfat" PTTYPE="dos" PARTUUID="e1d2cc2e-01"
/dev/loop2: TYPE="squashfs"
/dev/loop0: TYPE="squashfs"
/dev/mapper/ventoy: BLOCK_SIZE="2048" UUID="2023-04-21-10-04-39-00" LABEL="MANJARO_KDE_2210" TYPE="iso9660" PTTYPE="dos"
/dev/sda4: BLOCK_SIZE="512" UUID="5C4A12DA4A12B12E" TYPE="ntfs" PARTUUID="db256416-9e5a-4371-bf54-4af794fa8592"
/dev/sda2: PARTLABEL="Microsoft reserved partition" PARTUUID="1f438744-fc0e-47bf-99c1-b0a9daaadd8b"
/dev/sda9: LABEL="DELLSUPPORT" BLOCK_SIZE="512" UUID="30BAFF28BAFEE8EC" TYPE="ntfs" PARTLABEL="Basic data partition" PARTUUID="2d201cfe-fcfc-4ed4-dfc6-a2d70baac3c5"
/dev/sda10: UUID="ece49b76-595d-40cd-820a-29968c879e55" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="526cfc72-b71b-49fc-b493-b9989672fdc4"
/dev/sda7: LABEL="root" UUID="4fb222bb-cc4f-4803-a376-819e074d82c4" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="b19f4e80-3920-489e-aa8e-2b59c541b6b6"
/dev/sda5: UUID="EF17-3935" BLOCK_SIZE="512" TYPE="vfat" PARTUUID="16d2372a-d15b-4a9b-a38a-ee6fbad50cd5"
/dev/sda3: BLOCK_SIZE="512" UUID="FA3A68C23A687D8F" TYPE="ntfs" PARTLABEL="Basic data partition" PARTUUID="1aaceda7-f394-40a1-97b2-7bca35b900d3"
/dev/sda1: UUID="8415-4124" BLOCK_SIZE="512" TYPE="vfat" PARTLABEL="EFI system partition" PARTUUID="87a8d5f8-bee5-47b4-a79a-99211e0aa5d8"
/dev/sda8: LABEL="home" UUID="a3dc1290-4cd8-4e21-8d9f-d4946224c56c" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="133ec821-7d22-461e-a654-678116957171"
/dev/sda6: UUID="e9fe1e37-91cc-4933-8ab7-2dba61c68e4f" TYPE="swap" PARTLABEL="swap" PARTUUID="9537c565-d837-4759-987d-b091574c99a8"
/dev/loop3: TYPE="squashfs"
[manjaro /]#
Have you done some change to your system? When you do a manjaro-chroot -a, it tries to mount an EFI partition (ESP) with UUID F1D6-9A8A, but the actual one is 8415-4124.
You have to edit the /etc/fstab file of your Manjaro. You probably can do it from your liveUSB (from the file manager of the desktop environment), before chrooting to Manjaro. You have to replace the old UUID with the new one in that file.
After replacing the UUID, you can chroot again and reinstall grub.
I try, thanks. Done, now restart and see if everything is fine. Thank you.
Let’s do it from the terminal, it’s easier to give instructions
Chroot to your Manjaro with manjaro-chroot -a
Edit the fstab file with: nano /etc/fstab
This is a text editor that works with cursor keys. So move the cursor to the old UUID (F1D6-9A8A) and replace it with the new one (8415-4124). Then save and quit with CTRL-X. When it asks if you want to save, answer “Yes” and when it asks for the file name, just press ENTER
After that you can exit the chroot with exit and then you can chroot again, and this time it has to be able to mount the EFI partition and you can proceed to reinstall grub.
Ask again if something is not clear
Edit: I didn’t noticed that you were finally able to do it by yourself 
I did it, thank you very much!