You could also get cling on window treatments. Like this

There was a post awhile back that had this specific cling which made pretty rainbows. But they also make stain glass looking ones too or just cloudy ones (since I know you said you want simple). We use them in our bathroom windows and they work pretty good. Although we have to replace them every few years since the steam makes them un-cling. Then you could add heavier linen curtains if you wanted.

Another option add roller blinds with curtains over them. Example my bedroom (These are old pics. Ive since bought wider blinds so the sun doesn’t shine though. Ive also adding sting lights draped around curtain rod.) These specific roller blinds, are Ikea’s blackout smart blinds, that connect to my smart home and Alexa and are quite expensive, but you could add just some basic ones if you’d like.

Edit: that post I was talking about.