Any old bike will do, but keep
In mind alloy handlebar, stems and any other stainless steel thing connecting with alloy will be susceptible to corrosion. Especially alloy handlebars!
2 tips:
- buy a cheap carbon handlebar, swap this for the alloy one. (Google: galvanic corrosion handlebar)
- use Tef-gel (marine grease) on any bolt that needs to be adjusted and/or tightened
But any bike where you can swap these out for standard non proprietary parts will do.
Great idea to give an older bike a new life as designated trainer bike👌