>>106438188 (OP)
OP, while Signal is good for non-technical family, please consider using XMPP instead of Matrix. Much like the Web, Matrix is a complicated protocol that is nearly impossible to implement completely or correctly. This has led to the founders, who started a company called Element, leaving the community with a largely insecure and unusable Synapse implementation while their paid proprietary business/government Synapse gets all the updates. Additionally, at a protocol level, the "everything-as-a-room" architecture leads to slowdowns at best and breaking rooms at worst.
The extensible nature of XMPP counters this. Unlike Matrix, multiple independent server and clients exist that are implemented completely and correctly, but I would recommend Prosody as a server (it's super lightweight and easy to run) and Gajim, Conversations, and Monal as possible clients.