Can the new owner make me sign a non-compete I never had before?

Generally, no. Since October 25, 2021, Ontario's Employment Standards Act, 2000 has made non-compete agreements with employees unenforceable in almost all situations — a business changing hands doesn't create a new opportunity for an employer to lock in restrictions on an ordinary worker that weren't there before. There are two narrow exceptions: a business seller who becomes an employee of the buyer as part of the sale can still validly agree to a non-compete tied to that sale, and a defined, senior executive role can be asked to sign one.

Neither exception is about a regular employee simply continuing to work for a new owner after the sale of the business they already worked for. If you're being asked to sign a non-compete and you're not the person who sold the business, and not in one of those narrow executive-level roles, that request is very likely unenforceable even if you actually sign it.

That doesn't make refusing outright entirely risk-free for your job security, so if you're pressured to sign, get the document and your actual role looked at before agreeing to anything — and know that agreeing under pressure doesn't automatically make an otherwise-void clause enforceable.