Best free or cheap CRM when sales/money isn’t involved?

I am on a tiny team and want to consider using a CRM for managing relationships with our stakeholders. For reference, we are basically an information service and hold online and in-person events, manage contact with other similar groups and networks, but we don't sell anything, so a lot of the tools of CRMs don't apply to us.

I don't need to log every call or set up goals to "convert" anyone, but rather want to manage between us few coworkers our institutional relationships with both people and their organizations. It would be nice to basically have a way to keep a running list of who has attended what event, what topics people have expressed interest in, when our last major contact with a certain organization was (meaning, I would manually go in and flag it when we have a substantial conversation with a group, so that I can look back and say "Hey, it's been over a year since we contacted group X, or any group from region Y," for example).

It may be counterintuitive but I actually don't prefer any product integration. Just a standalone application or website. Not sure if there are free or cheap tools out there, but I might as well ask here! I am thinking of simultaneously asking in /r/Excel if it's feasible to use a spreadsheet in Excel or Google Sheets as a sort of master contact list to achieve a similar function, for the main reason of being free and being simple (in the sense that we already deal with spreadsheets a lot and, if using Google Sheets, our backend is Google Workspace, so it would integrate well into our daily routines). I know it's generally advised to not use spreadsheets as databases but for our somewhat simply needs I want to pick the brains of both subs. Thanks!