I have been using RSForms for many years, hence why i purchased RSDirectory, because RSForms is good with compatability.
But when it comes to support, yes, they "like to use the contact the template supplier" card with every support ticket. Their support staff just say "Check the Joomla default template, it works there"...
It is no use i argue with them anymore, as it is just pure frustration... I dont think RS Directory is as big of a seller as RS Forms, hence why they do not develop it beyond Bootstrap 3:
The discrepancy is rather normal since you're mixing multiple frameworks. As previously explained RSDirectory! has been designed to use the same Joomla! 3 Bootstrap 2.3.2 framework and your template loads Bootstrap 5 instead.
Our products have been designed to utilise what the Joomla! CMS provides by default. Currently, Joomla! 3 natively supports Bootstrap 2.3.2, thus the products being designed to work and use this particular framework as well.
Unfortunately some template developers don't understand on using what Joomla! provides by default and insist on using unsupported backward incompatible versions. Yes, your template may look nice because it has Joomla! content customized, but add any other extension that was designed on the same Joomla! Bootstrap and you'll end up with similar issues.
The idea of Bootstrap is to use it as a foundation and add styles on top of that. This is so developers can focus more on writing functional code rather than on styling their extension(s) - and so that every extension "blends" into your existing template / styling, instead of each having their own unique design and making the website look made out of all these different "parts" stitched together. At least that's how it was supposed to be used.
Sadly, nobody in the template business followed that. Everybody added their own framework (take a look at how many are there, almost every template developer went with their own version), created overrides or workarounds (such as Bootstrap 2.3.2 definitions inside their CSS files), even for basic Joomla! components (look inside your template's "html" folder - you'll see overrides for these). Now, how can somebody expect extension developers to provide overrides for their own template, when these files are actually placed in your template's structure and they are specific to whatever framework the template developer chose?
We've always tried to use the Joomla! framework standards - that's why our products are using whatever Joomla! supplies. If you want to have RSDirectory! run on Bootstrap 5, then consider upgrading to Joomla! 4 as it would then use what the Joomla! 4 framework supplies.
** I will now update to Joomla 4, at the cost of some components, and when doing so, it even states SP Pagebuilder and RSDirectory is not compatable with joomla 4, even though it is the latest 3.8.3 version :) ...