I have made a test on my side and don't have the issue that you mentioned. The screenshot as below:
I could not reproduce your issue on my side currently, please check if you have disabled the "Attachments to list items" option within Advanced settings of the List Settings as below:
If you have disabled the "Attachments to list items" option, please enable this option on your side, then refresh the SharePoint list data source within your PowerApps app to check if the issue is solved.
More details about disabling or enabling "Attachments to list items" option within SharePoint list, please check the following article:
In addition, please take a try to re-create a new SharePoint list and a new PowerApps app on your side, then add this SP list into your PowerApps app as a data source, then check if the issue is solved.
Already did all that and I also try it with my SharePoint online environment and with SharePoint online works the problem is with my on-prem SharePoint 2016 using a custom list.
Okay, nevermind, I have the answer I needed, by @v-xida-msft but on another post :
Attachments seems not to be a feature available for On-Prem SP datasource.
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