Jetbrains Upsource code-review system alternatives?

We are currently not able to adopt a pull-request based workflow due to multiple reasons (among having several legacy code bases). Upsource is no longer sold by Jetbrains, they are not willing to sell us additional licenses nor giving additional user licenses.

Jetbrains offers Space to us as an alternative but it is (1) expensive, (2) tries to do much (planning, source control and project management we already have tools for which work perfectly fine).

What are similar products to Jetbrains Upsource?

For those who don't know: You can either do a branch code-review, or add individual commits and the tool will keep the code-review up to do with additional commits referencing the same JIRA-ticket/user story number/etc. Then as in any code review system you can put overall review comments or per line, etc.