• Yes that is a CRT
• HDMI to 3.5mm antenna is a non-existant connection and I will explain why and what you need to do.
• You will not like the look of any HDMI signal onto that tiny and cheap CRT (I own this TV and know)

Okay so any signal over HDMI is a digital signal, CRTs operate using only an analog signal (for the most part, there are some later digital sets). You would need to put your HDMI signal into a converter like this one. This transforms the signal into RCA/Composite. Then you take that signal and run it into one of these and then on the side that says To TV you put a coaxial cable from there to one of these. Then you take that and plug it into the 3.5mm antenna plug on the side of the TV.

I'm planning on getting some bookshelf speakers (Edifier R1700BT) with two RCA inputs for my PC/TV setup but my outputs are only 3.5mm (PC) and HDMI ARC (TV)

The 3.5mm issue can easily be solved with a 3.5mm to RCA connector but I'm not sure with the HDMI ARC one.

Would an HDMI ARC to RCA connector easily solve my issue or are there nuances I need to watch out for?For example, HDMI to 3RCA cable or HDMI to RCA Converter.

Is the converter better or should I just stick to the cable since the speakers would have their own power anyway?

Thanks