What're some cheap (and private?) ways I could hold onto legacy phone numbers?

I have a legacy number that I need to hold onto. Currently, I’m paying for an expensive Canadian phone plan and I’m using it on a SIM card in an old smartphone, but I was wondering if there are any cheap options that would allow me to maintain ownership over a phone number. Ideally with the ability to access it across devices, rather than having to dedicate an old smartphone to it.

I’ve been struggling to research the subject myself, so I’m asking here because I know a lot of people use VoIP services and it’s my understanding that some VoIP services could offer a more private and cheap(er) solution to owning a phone number, so I was curious if anyone had any recommendations.