Succeeded fixing my problems while staying with lirc by following @anon88919003’s advice on this very forum (Logitech Harmony Setup), i.e.:
- Setting all delays of the
Microsoft Media Playerdevice to0 - Adding
/storage/.config/autostart.shwith:
ir-ctl -t 50000
ir-keytable -D 375 -P 100
With these change, my Harmony One is as at least as responsive as it used to be with LibreELEC on my i5 Haswell NUC.
Again, kudos and thanks to @anon88919003 for the "lirc solution" to the problem.