Allira
You don't lose British citizenship (although it could be taken away in rare circumstances) but, if you want to come into the UK on a foreign passport, an ETA is now required.
It's easily done, I would think, we have to do them for Australia.
We, Brits, have to have visas of some type for many countries, it’s really not a big deal, an ETA is simply a form of visa and will be easily and cheaply obtained.
Honestly I cannot see the issue? I was born in Singapore to service parents, my mother was British and my biological father Canadian, I chose to only have British citizenship therefore on our trip to Canada last year had to get electronic visas. I’m not really sure what all the fuss is about, on the one hand we tell the govt to put in more checks then when they do, that’s also wrong! It’s a bit like the angst around ID cards and having to show photo ID at polling stations, honestly big fat fuss over nothing, in my opinion.