I am absolutely certain you can port your number in the same way you can with a mobile. Obviously, you can't port it to a copper lined analogue supplier who uses the Openreach Network due to a stop sell of all all-copper products from Openreach.
Who you go with depends on how you want it plugged in at your end. If you want the phone plugged in to your router directly, you may end up having to use an ISP that provides a router capable enough - most do now as Digital Voice is the only future for fixed landlines.
If you don't mind an external adapter, you can pick any Digital Voice supplier, or SIP supplier, with the phone plugging into the adapter, and the adapter plugging into your wired network (WiFi isn't ideal). Generally, better deals can be had by not taking out the DV service with your ISP, and shopping around.
If you have a SIP phone, unlikely now, but you may in the future, it can just plug in your network.
I've been using a SIP provider for over 20 years, mine is free rental (though this is no longer offered), about 1p per min to landlines and 11p per min to mobiles, and around 1.5p per min to my relatives the other side of the pond.
Downsides of these systems enforced upon us is they are reliant on electricity and a working, good, stable internet, whereas a traditional phone line isn't. Most exchanges, even most of the small ones had batteries and small generators to keep the exchange up and running during power cuts, and providing enough power for non-cordless phones.