What was ++Lefebvre's relation with Eastern Catholics?

Probably very little!  I know of no writings or recordings where he mentions them. 

I thought ++Lefebvre spoke with eastern schismatics, and they said they would return to communion with the Catholic Church if Modernist Rome converted and became liturgically like the SSPX.

It would be good to get a citation for when and where he said this, and with whom he spoke.  That would be golden.  I have to think that the Orthodox view the whole Novus Ordo thing as a joke anyway. 

There are Orthodox jurisdictions where they use a form of the Gregorian/Tridentine Mass (both Latin and vernacular as the case may be), but of course they have to put their own stamp on it, removing the filioque, making the epiklesis more explicit (because they're convinced that is the point at which the bread and wine become the Body and Blood of Christ, but then again they come back and say "why is it important to know that?"), and most bizarrely of all, pressing leavened bread down into a wafer-like disc rather than using unleavened hosts.  They've got this thing about "azyme" bread.

To my knowledge, though, nowhere in Orthodoxy do they attempt to recreate the Novus Ordo.  They've got too much sense to do something like that.

I thought ++Lefebvre spoke with eastern schismatics, and they said they would return to communion with the Catholic Church if Modernist Rome converted and became liturgically like the SSPX.

Same here, I recall that connection, but to find that quote in the 300 conferences of ++ L is unlikely. SSPX's eventual treatment by Rome was carefully observed by the Orthodox - like a LITMUS TEST. Just as the SSPX represented the "Conservative " rite in the Latin world, the Orthodox ARE the conservatives, albeit schismatics.
Anyway, here is a good article re: the Russian Orthodox vis-à-vis SSPX/  Vatican II Rome. 
(Torching Catholics who won't join Orthodoxy! in Ukraine)
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Excerpt:
https://opuspublicuм.com/russian-orthodoxy-and-the-sspx/

"...Even if the Russian Orthodox come to adopt some modifications to their liturgical praxis, they will no doubt be minor and demonstrate nothing close to the radical deviations found throughout the post-Vatican II Roman Rite. Contemporary Catholics who trumpet the “virtues” of the Novus Ordo Missae would quickly find themselves being shown the door if they brought those views into Russian Orthodox circles—and rightly so. The late Patriarch of Moscow, Alexi II, openly praised Summorum Pontificuм and the liberation of the Tridentine Mass. It is hard to imagine how the Russian Orthodox liturgical mindset, which is arguably even more conservative than the SSPX’s, could get a free pass from the Society’s critics, many of whom believe that the watering-down of the Roman Rite has been a positive development for the Catholic Church.

Second, as we have seen in post-Soviet Russia (and certainly in pre-Soviet Russia), the Russian Orthodox have little time for religious liberty. Although the Russian state officially tolerates non-Orthodox Christians and other religious minorities, Orthodoxy remains the openly favored confession—and that’s unlikely to change anytime soon. Moreover, the situation in Ukraine (specifically the Crimea) reveals that the Russian Orthodox Church is not above using military force to drive out other Christians groups such as the Ukrainian Greek Catholic Church. This attitude is consistent with historical Russian Orthodox praxis which, inter alia, included violently converting Greek Catholics to Orthodoxy, burning Old Believers alive for making the Sign of the Cross with two fingers, and driving Jews out of the country. Whatever one thinks of the SSPX’s criticisms of religious liberty, specifically the docuмent Dignitatis Humanae, they pale in comparison to the living reality of Russian Orthodoxy on its native soil.

And last, despite occasional appearances to the contrary, the Russian Orthodox Church is rabidly anti-ecuмenical. No pope has been allowed to visit Russia or meet with the Patriarch of Moscow, and Rome/Moscow relations have been at a standstill for some time. Some have gone so far as to charge the Russian Church with being disingenuous on ecuмenical relations, claiming, on the one hand, that it wants to find practical ways to work with Rome while, on the other, looking for any excuse to halt participation in Catholic/ Orthodox rapprochement efforts. As for non-Catholic Christians and non-Christians, the Russian Orthodox Church remains, at best, leery. There is not a single criticism of ecuмenism the SSPX holds which, by their lights, the Russian Church could not accept and vice versa. If the Society is backwards, unenlightened, and outmoded in its views on other religions, so is the Russian Orthodox Church—so why does it get a free pass on this and the other aforementioned matters?..."