Problem compiling source (undefined reference) on latest lazarus

[th3bucch]

Hello,
I was trying to compile transgui without success on a new system with a fresh install of Arch (KDE).
Both AUR packages transgui-qt and transgui-gtk, which I previously used on Manjaro, are now failing to compile.

I then tried to compile directly cloning this repo, but it still fails in the same way, with identical errors.
Here I attached a file with the full output: transgui-dump.txt
I can't figure out if it's a dependency problem or just source not working on latest compilers.

Using the released binary (or transmission-remote-gui-bin from AUR) is not possible since I'd get same errors as #1241

Any help will be appreciated, thanks.

UPDATE:
I tried compiling on a laptop with Arch that was not updated since a few days, it still had lazarus version 2.2.4. There the compile was successful. As soon as I updated lazarus to latest version (2.2.6) together with these packages I started having the same issue as above.
Downgrading only lazarus to 2.2.4 makes it work again.

Info:

1. Operating system: Arch Linux
2. Transmission Deamon: 3.00
3. Transmission Remote GUI: 5.18.0 and latest git

[fredo-47]

Maybe this is helpful related information:
When I build the fork of xavery, which installs the latest fpc (3.2.3) and lazarus (2.2.6), building of this original transgui here also stops with errors.
Only after I deleted the file fpc.cfg (which contains path to custom lazarus installation), building of original transgui here works again, then with original lazarus 2.2.4.

(on Linux Mint 21)