In Finland the collective-agreement that covers IT work defines this. The way I've been paid has been the same across several companies:

You get paid 50% of your normal hourly salary for every hour you're "available".

You get paid 200% of your normal hourly salary for every hour you're working on an issue, incident, outage, or problem.

So being on-call is pretty lucrative, given that you'd usually do it for a seven day period. (i.e. 9am Monday to 9am the following Monday.)

Australian Team, We get $20 per day (pre tax) oncall allowance, then time and 1/2 for any work done, time calculated to when you can go back to doing what you were previously. Generally works out to a minimum of 30 minutes overtime for any calls.

If you don't get 10 hours continuous break before the next work day, you fall into fatigue leave and either get paid overtime for the next days work or are stood down till you have had a 10 hr break.

Still doesn't stop our operations team being completely snowed with both workday and oncall work, but they can make a fairly good bonus wage out of it.

Your ops team might be at my old employer. Ops team had the above benefits but no one in SaaS Engineering (devs) got anything as second level support.

Yeah, we seem to contract second level support from the lowest bidder. Tick, we have a support contract, regardless of how dubious it's value.

We get a flat ~800$ for an on call week (Thursday to Thursday) and Friday is off. Nothing extra for working night, but you’re not expected to work a full day if you had an incident the night before.

At my previous employer we got $4/hour for every hour on call outside normal business hours. So $64 per work day or $96 on a weekend or holiday or $512 for a typical week. Paid quarterly.

One of my reports pointed out that he made more from on call each year than the difference between an average and outstanding performance bonus. He wasn’t wrong.

$35 per day for me. 1.5x for the first 3 hours. 2.5x for every hour after.

Minimum call out fee of 2 hours regardless of the length of the call.

Also in Australia. This only started when I joined as an SRE.

Prior to that the Devs just said no it'll stay broken till we come back to work and that was largely acceptable. The on call rates only started as our reliability became more of a business need.