What AI conferences in Europe should I consider submitting papers to explaining the ongoing work on RefPerSys? https://afia.asso.fr/journee-hommage-j-pitrat/ is a seminar on March 6th, 2020, in Paris (France, European Union), in honor of the late Jacques Pitrat, who advocated during all his professional life a meta-knowledge and reflective approach. (You need to register to attend that seminar).

Pitrat's blog is available (in spring 2020) on http://bootstrappingartificialintelligence.fr/WordPress3/ (and some snapshot of his CAIA system is downloadable here - but no documentation; however you might try to type L EDITE on stdin to caia). He wrote the Artificial Beings : the conscience of a conscious machine book describing the software architecture of, and the motivations for (some previous version of) CAIA. See also this A Step toward an Artificial Artificial Intelligence Scientist paper by J.Pitrat.

What AI conferences (or AGI workshops) in Europe should I consider submitting papers to explaining the ongoing work on RefPerSys?

That RefPerSys project (open source, open science, work-in-progress, with contact information) is explicitly following J.Pitrat's meta-knowledge approach. Feel free to follow or join that ambitious open-source (actually free software) project.
Probably to as many as possible. Average accept rate of papers is around 20%. You can find the best conferences on AI &amp; ML Event.