IMX8MP simple-audio-card (MAX98357a) convert-rate not working

Question

I'm working on a custom board on IMX8MP, with STM32 I2S internal DAC as audio card (outsorced, so I can't do too much about how it works). For that purpose I've created simple-audio-card config based on the MAX98357a driver. It works, it's capable to sand audio over I2S to the recier at 48000Hz, stereo. here's my device tree config:

    codec_ext: max98357a@0 {
        compatible = "maxim,max98357a";
        #sound-dai-cells = <0>;
    };

    sound {
        compatible = "simple-audio-card";
        status = "okay";
        simple-audio-card,name = "Muminek";

        simple-audio-card,format = "left_j";
        simple-audio-card,bitclock-master = <&dailink_master_cpu>;
        simple-audio-card,frame-master = <&dailink_master_cpu>;
                simple-audio-card,convert-rate = <44100>;
                simple-audio-card,convert-channels = <1>;

        simple-audio-card,codec {
            sound-dai = <&codec_ext>;
        };

        dailink_master_cpu: simple-audio-card,cpu {
            sound-dai = <&sai3>;
        };
    };

        pinctrl_sai3: sai3grp {
                fsl,pins = <
                        MX8MP_IOMUXC_SAI3_TXFS__AUDIOMIX_SAI3_TX_SYNC   0xd6
                        MX8MP_IOMUXC_SAI3_TXC__AUDIOMIX_SAI3_TX_BCLK    0xd6
                        MX8MP_IOMUXC_SAI3_RXFS__AUDIOMIX_SAI3_RX_SYNC   0xd6
                        MX8MP_IOMUXC_SAI3_RXC__AUDIOMIX_SAI3_RX_BCLK    0xd6
                        MX8MP_IOMUXC_SAI3_RXD__AUDIOMIX_SAI3_RX_DATA00  0xd6
                        MX8MP_IOMUXC_SAI3_TXD__AUDIOMIX_SAI3_TX_DATA00  0xd6
                        MX8MP_IOMUXC_SAI3_MCLK__AUDIOMIX_SAI3_MCLK  0xd6
                >;
        };

&sai3 {
    assigned-clocks = <&clk IMX8MP_CLK_SAI3>;
    assigned-clock-parents = <&clk IMX8MP_AUDIO_PLL1_OUT>;
    assigned-clock-rates = <24576000>;
    pinctrl-names = "default";
    pinctrl-0 = <&pinctrl_sai3>;
    fsl,sai-mclk-direction-output;
        #sound-dai-cells = <0>;
    status = "okay";
};

However, they want to get 44100Hz and mono in left channel. Currently if I play mono, it goes to right channel only (for "left_j" default mono channel is inverted).

I've been trying to use:

simple-audio-card,convert-rate = <44100>;
simple-audio-card,convert-channels = <1>;

But no luck. I've got a feeling it's missing simple-audio-card,routing or simple-audio-card,widgets, but can't get any detailed info on how to configure those. Any help would be highly appreciated. Thanks in advance!