Selfhosted CA integrated to the system aren't reconised

[Astaoth]

Steps to reproduce

1. Make a custom CA
2. Integrate this CA into the Linux CA store (on the server and the client sides).
3. Test this CA integration with multiples services in order to validate its integration
4. Deploy a selfhosted Synapse server following the official guides
5. Make a tls key/certificate for Synapse from the local CA
6. Configure Synapse for using the fullchain certificate made
7. Launch Element-desktop and try to make an account on the selfhosted Matrix/Synapse server

Outcome

What did you expect?

Being able to connect to my selfhosted Matrix server.

What happened instead?

I'm not able to connect myself to my selfhosted server. When running element-desktop from a terminal, I've this error : "ERROR: VerifySignedData failed". The CA is known and integrated to the system CA store.

NB : if I configure Synapse for using the final TLS cert only and not the fullchain, I've this error : "ERROR: No matching issuer found". This seems normal as I've an intermediate CA, which needs to be provided to Synapse.

Operating system

Arch Linux

Application version

1.11.65-1

How did you install the app?

from package manager : pacman -S element-desktop

Homeserver

Selfhosted debian server : matrix-synapse/stable-backports,now 1.95.1-1~bpo12+1 amd64

Will you send logs?

No