Sorry ya we need 3rd party domains at least for images so the costs are not crazy with caching/proxying. Maybe just turn it off just for Swurl?
And for your reference, i enabled googletagmanager in uMatrix, but it still got blocked by uBlock origin. I suspect even if i were to disable both uMatrix/uBlock origin extensions, then my pihole would still block it.
As per using caching proxies , use dns cname. So security conscious people / paranoid configurations know that the caching proxy is in your control and wont leak cookies from other domain accesses. So define something like pix-cdn.swurl.com or static.swurl.com .