In a lecture meant for his inauguration at the University of Leiden in
1920, Einstein remarked:

"...we may say that according to the general theory of relativity space
is endowed with physical qualities; in this sense, therefore, there
exists an ether. According to the general theory of relativity space
without ether is unthinkable; for in such space there not only would be
no propagation of light, but also no possibility of existence for
standards of space and time (measuring-rods and clocks), nor therefore
any space-time intervals in the physical sense. But this ether may not
be thought of as endowed with the quality characteristic of ponderable
media, as consisting of parts which may be tracked through time. The
idea of motion may not be applied to it."

Shortly before his lecture in Leyden in 1920 he admitted in the paper:
Grundgedanken und Methoden der Relativitätstheorie in ihrer Entwicklung
dargestellt:

"Therefore I thought in 1905 that in physics one should not speak of the
ether at all. This judgement was too radical though as we shall see with
the next considerations about the general theory of relativity. It
moreover remains, as before, allowed to assume a space-filling medium if
one can refer to electromagnetic fields (and thus also for sure matter)
as the condition thereof ".

Perhaps he was correct, you think?

JS