Xcode comes with Simulator developer.apple.com/library/content/documentation…
The modern.ie site still offers free, short-lived VMs for desktops: developer.microsoft.com/en-us/microsoft-edge/tool…
If you're lucky there may be an open device lab in your area: https://opendevicelab.com
If you genuinely only need access for a short time, pretty sure Saucelabs and Browserstack both offer a free trial which might be just enough to get this bug tested.
I will say though: the time you'll spend avoiding the fee is likely to cost more than a month's access to Browserstack, so it makes more sense to just pay the fee and get the work done.
Sounds a lot like the project should have it built in as a cost/overhead. If the bug isn't worth $39 for the month of Browserstack access, then I'd be asking if the bug needs to be fixed at all.