The simple solution is to use another cloud, such as proton drive mentioned below.
Another more technical solution is to setup a vpn at home and use vpn + smb to share files with your phones, this one fails if your computer isn't always online at home or if your internet provider runs CGNAT.
Your computer could be replaced with a selfhosted solution as nextcloud running on separate hardware, but now we're firmly in selfhosting land.
The VPN home could be replaced with a VPS that both your home network and mobile devices connect to as a CGNAT workaround.
The KISS (Keep it simple, stupid) principle says that getting another cloud storage is the way to go. If you truly wanna own your cloud then a trip to selfhost land it is.