Wintermondnacht wrote on 06/24/24 at 08:51:56:

I would certainly think of 7. c5 as suggesting itself. Curiously enough, back in the first edition of ECO-A in 1979, Gufeld gave it as leading to an edge for Black (citing F. Portisch-Ozsvath 1967).

(historical notes)

After 1. d4 Nf6 2. c4 d6 3. Nc3 Nbd7 4. e4 e5, I see (in the non-subscriber material) that Nigel Davies indicates 5. d5 as the "main problem"/"key issue" with Black's move order. That took me back to NIC Yearbook 5 from 1986, in which a game between Tony Miles and IM Bernd Stein was highlighted. "In this opening, White's traditional plan is to develop his king's bishop to e2 or g2 and maintain the tension in the centre as long as possible, but Miles snapped his fingers at this 'tradition' in a game against Stein where he played the very unusual 5. d5 and got a good position."

I see that Miles had previously played 5. d5 against Mestel in 1984 and against Rubinetti in 1979. (He won those games too.)

A player I recalled as favoring 3...Nbd7 is Andrew Soltis. I see that he had a game 30 years ago (against GM Jonathan Levitt) which was essentially the same as Rapport-Markus until move 15. (That game, too, was won by White.)