Two French Radios

[19and41]

That is indeed good advice.  The paper and electrolytic (chemical) capacitors can fail abruptly and can at a minimum allow noise from the mains AC voltage to get into the audio.  This is a website that has information on the identification and replacement of such capacitors.  https://antiqueradio.org/welcome.htm  I usually recommend it to folks starting out.  I wouldn't want to have the radio surprise you with a popped capacitor.

[countryman]

That "pop" can be like "ka-woooom"at times ;-) and it can ruin some hard to replace components like tubes or transformers.
It looks like FABphones bluetooth add-on gadget includes an audio amplifier and does away with all the old circuitry? That would make it easy to connect, but also takes away the unique tube sound and feeling. You can't have it all...