OK - I've now loaded the Beta version and it appears to recognise Bold fonts, so I'll go with that for a while.
(If I have any issues, I can always have my old MacBook ready as a backup for live services.)
Before I loaded the Beta, I compared all the settings against my old MacBook (MacOS 10.11) and noted one anomaly - in the Players section on the new Mac it shows "VLC (unavailable) NOTE: To use VLC you must install the 64bit version". Now my 2.4.6 install must have been 64bit as Rosetta won't translate 32bit Intel apps - but this definitely suggest that the translation through Rosetta for the M1 chipset is throwing some system detection stuff off.
I appreciate that the devs won't have M1 chipsets yet and so a Universal version of OpenLP (with native Apple Silicon support) may be a while off - and will probably only be in the 3.0 release and not the 2.4 branch. But hopefully this information will help any other queries until then.