for me:
gnutls-cli --tofu aur.manjaro.org
...
- Status: The certificate is trusted.
Host aur.manjaro.org (https) has never been contacted before.
Its certificate is valid for aur.manjaro.org.
curl -Iv 'https://aur.manjaro.org/packages-meta-ext-v1.json.gz'
...
* Server certificate:
* subject: CN=1715854792.rsc.cdn77.org
* start date: Apr 27 17:10:39 2023 GMT
* expire date: Jul 26 17:10:38 2023 GMT
* subjectAltName: host "aur.manjaro.org" matched cert's "aur.manjaro.org"
* issuer: C=US; O=Let's Encrypt; CN=R3
* SSL certificate verify ok.
My script return error (only) sometime , the same error as you, 3 times out of 10
So, is a random libsoup bug 