There are, indeed, scriptures that speak contrary to the fairly modern phraseology of "a pre-tribulation rapture". But it is not the two asked about here. That is because, when Jesus addressed those two verses to his disciples (Luke 17:22), neither he nor any of his disciples had ever uttered such a phrase. And the context shows what the warning of those two verses was about.
Jesus was warning about future events, foretelling the awful destruction of Jerusalem (which happened within the generation of those who heard him). That is why his first warning, about people being destroyed as were the people in Noah's generation, due to taking no note of his warnings and ark-building, is so powerful. With that in mind, he then gave a similar warning lesson from history. This time it was when Lot and his daughters fled Sodom and area, but his wife disobeyed the warning by turning around while fleeing for their lives to look back on all the destruction. She died as a direct result, as did all those in Sodom and area.
"Even thus shall it be in the day when the Son of man is revealed. In
that day, he which shall be upon the housetop, and his stuff in the
house, let him not come down to take it away: and he that is in the
field, let him likewise not return back. Remember Lot's wife." Luke
17:30-32 A.V.
Now comes verse 23, which is most certainly directly linked to the first warning from history - people ignoring it in Noah's day - and the second warning from history - people ignoring the latter, equally deadly warning.
"Whoever shall seek to save his life shall lose it; and whosoever
shall lose his life shall preserve it."
This is directly linked to Jesus' words earlier on, when he put this the other way around, and in the context of his disciples being sent out to preach as sheep among wolves; of being persecuted and delivered up by strangers, relatives and friends. Jesus said:
"And fear not them which kill the body, but are not able to kill the
soul: but rather fear him which is able to destroy both soul and body
in hell... He that findeth his life shall lose it: and he that loseth
his life for my sake shall find it." Matthew 10:28 & 39 A.V.
Those two related passages speak of all and any Christians being prepared to lose their physical lives for Jesus' sake, in all and every generation. Yet they will have eternal life secured unto them by what Jesus did. That is why they have no fear of what man might do to them. Persecution of Christians will reach a climax before Jesus suddenly returns to instantly usher in the Day of Resurrection and Judgment. Revelation and other texts are clear about that.
It really is only since the teachings of J.N. Darby, W. Kelly and A.P. Scofield gained ground from the 1830s on that talk of "a pre-tribulation rapture" has taken hold in some quarters. There is no need to go into any of that here, for the question only asks about two verses in Luke's gospel. Sticking purely to the verses in question and checking context, the answer indicates that neither speaks about any "pre-tribulation rapture". That being the case, it is up to those who believe this comparatively recent teaching, to explain how they might think about any contradiction, or not. My answer is that two verses which have got nothing to do with any supposed "pre-tribulation rapture" cannot contradict such a notion any more than they can support it.