The plug-ins are found, but won't load with my version of Gajim.

--8<---------------cut here---------------start------------->8---
11/19/20 15:10:01 (W) gajim.plugin_system        Plugin omemo not 
loaded, newer version of gajim required: 1.2.91 <= 1.2.2 <= 1.3.90
11/19/20 15:10:01 (W) gajim.plugin_system        Plugin openpgp 
not loaded, newer version of gajim required: 1.2.91 <= 1.2.2 <= 
1.3.90
--8<---------------cut here---------------end--------------->8---

This is on current master.  How are these plug-ins expected to be 
used?

> -       (variable "GAJIM_PLUGIN_PATH")
> +       (variable "PLUGINS_OS")

This doesn't look related to the fix at hand.

Why remove GAJIM_?
Why rename _PATH?
TBH, both strike me as unnecessary regressions.

Kind regards,

T G-R