In the US, wired phones were often leased from the phone company! If you shop for vintage phones from the 1960s, they will often have a decal to that effect. Examples:

https://i.ebayimg.com/images/g/71gAAeSw1URp8QPF/s-l1600.webp

https://i.ebayimg.com/images/g/tPAAAeSw~RxqBiLR/s-l1600.webp

I think this started to change only in the 1980s and 1990s, thanks to cheaper electronics imported from overseas?

N900 days. Damn I still miss that device :(

In 2008 I've got a Neo Freerunner, a few years later a Nokia N900, then a Librem 5. So at least the last 18 years, I guess? We need to work hard for it to keep going though.

(well, unless we start to bikeshed on the exact meaning of "fully control")

I wasn't alive in the 90s, so for me it was 2012-2015. Android was pretty open, iOS was easier to jailbreak, and the ecosystem felt a lot "freer" than today where you step outside of Google or Apple's garden and get endless Cloudflare captchas, apps refuse to load due to attestation, and things are designed without privacy in mind.