GlassWire is an excellent firewall, but way too expensive for the common user. Consider a joint venture for Protonmail/vpn customers or direclty buy the company :D
I don't know how it works with firewall really. But an extra protection to the phone/computer.
i would buy ProtonFirewall
Florence Janette McCoy commented
I like to be more secure
agree. It could be nice to be able to select which program is able to go through and if needed to do some traffic shaping