I also use KeepassXC and Synthing together and I am very happy with this combination.
One tip that I have, if you are worried about the security of the database file being shared, is to get 2 Yubikeys and use these, along with a strong passphrase, to protect the database file.
The only thing you should keep an eye on is probably the license? But I’m not the right person to discuss about licensing :/
It is normal practice to keep the same copyright notice and add your name to it, e.g for this project I forked in 2021: https://code.alienscience.org/alienscience/dnsclientx/src/branch/master/LICENSE
I do this for sites where I don’t care at all about security. One minor tip, that will protect against automated attacks if the password is cracked, is to add part of the website name into the password (e.g “mystrongp4ss!lemworld”) .
A human could easily crack it, but automated systems that replay the password on different sites would probably not bother to calculate the pattern.