We should raise our Python requirement so that we can make use of new features. The current requirement (Python 3.4.4) is lower than needed for currently interesting distributions.
Oldest interesting distributions, and their Python version: RHEL 8: 3.6.8 Ubuntu 22.04: 3.10.6 Debian 11: 3.9.2 SLES 15: 3.6.15
I think I found everything that should be updated. Tested that tl-setup still starts, and that the automatic tests don't complain.