There are some caveats. It depends on the age of the television. Some CRT TV can display a widescreen image and others may not. Anything going out through HDMI (on consumer products) is going to be widescreen by default even if it doesn't look like it is. Your CRT may show this image in widescreen (postage stamp) or smushed (with black bars on side aka pillarbox) but you aren't going to know unless you try some things out.
I made an Imgur post about using a PS3 to play a BD on 4:3 displays, one supported widescreen (consumer Trinitron) and one that doesn't mention it (PVM). It isn't exactly related to what you are asking about but it will show what some 4:3 CRT will do with a 16:9 video signal.
https://imgur.com/gallery/bluray-on-4-3-displays-dYkYhThere may be limited options in the TV OSD to handle this, such as having a zoom option but it may not work as expected or at all.
4:3 HDMI does exist, but it is additional equipment that is not documented because they are all for industrial/commercial. I've known about them for awhile but haven't gotten my hands on anything to play with. In any case, you want to be able to get the 16:9 into 4:3 which will require an external device and then the signal can be converted to composite or whichever. I don't think it matters which happens first, the aspect ratio or connection adapter but it may matter if a quality loss occurs.