Hi. This is really weird.
This package also failed for me on bookworm, with the same error which happened to Lucas (the one in the Subject). But today I tried again (in bookworm) and it worked, without any source change at all. (mricron version 1.2.20211006+dfsg-1). I see that this change was made to try to fix the bug: * Build-Depends: libx11-dev. Closes: #1026734 but libx11-dev was already being installed when the package was built: https://buildd.debian.org/status/fetch.php?pkg=mricron&arch=amd64&ver=1.2.20211006%2Bdfsg-1&stamp=1637004231&raw=0 (probably because of a build-dependency which in turn had a dependency on libx11-dev). So, even if adding libx11-dev was probably correct and formally necessary, as -lX11 was being used, I think it was not the real reason for the failure. (Cc to Lucas, just in case he reported similar bugs in other packages). Thanks.